Starting about 3 years ago I have converted most aspects of my reloading to metric. It started with overall lengths, for which mm (to one decimel place) is just about the perfect level of precision, and very intuitive.
I don't like digital scales, and I was aware that Ohaus used to make a metric version of the 5-0-5 balance beam scale but it was discontinued. It took some looking, but eventually I found a scale distributor in California that had some dusty old boxes on his shelf, and I cleaned him out. I may now be in possession of the only 505-10 scales in North America that are available for sale. Let me know if you want one.
Metric weights are starting to show up on factory ammo boxes (28g & 32g shotshell loads, and Federal puts bullet weights in grams on most of their ammo), but it isn't seen much on component bullets (yet). I usually refer to them without units ("a 147 FMJ bullet"). I have never seen charge weights published in grams. I usually consult a couple of manuals to get an idea of what window I expect to work in in grains, then convert to grams, round to something convenient, make the notes in my reloading notebooks and never glance at the published manual numbers again. Eventually the archaic units lose meaning to you. For example, I can tell you that my standard 5.56mm loads use 1.76g of WC-735, but had to punch that into a calculator just now to figure out that that was 27.1 grains.
It raises some eyebrows when I start chatting reloading with folks at the range, but whatever. I wasn't going to start choosing load data based on their say-so, anyway. I have posted bits of data here and over on the castboolits site, and nobody has chastized me for it yet.